1. Field of the Invention
The present invention relates to a projection type display apparatus such as a projector having a cooling means for cooling a light source as a light emitter. In particular, the present invention relates to technology for cooling properly the light sources of a projection type display apparatus using a plurality of light sources.
2. Description of Related Art
A projection type display apparatus such as a projector has been known as an apparatus for obtaining an image on a big screen. The projection type display apparatus modulates light from a light source lamp with a video signal so as to form an optical image and radiates, by using an image display device such as DMD (Digital Micromirror Device) or a liquid crystal, thereby projecting the optical image in a magnified manner on the screen by the use of a projection lens.
The light source lamp is filled with mercury, a rare gas, a metal halide and the like. When a predetermined voltage is applied to the electrode in the light source lamp, a discharge arc occurs and the filler gas inside the lamp is convected. The discharge arc is curved to form an arc due to the convection of the filling gas, approaches the top of the light source lamp, and thus the temperature of the light source lamp rises. If the temperature of the light source lamp rises extremely, problems such as whitening and life property degradation will occur. To the contrary, when the temperature of the light source lamp is extremely low, it causes problems such as blacking and degradation in the brightness of the light source. Therefore, temperature management of the light source can impose a great influence on the quality and reliability of the projection type display apparatus.
In particular, for an apparatus that uses a plurality of light sources for the purpose of providing a projected image with a high brightness (see JP 3581568 and JP 2000-171901 A for example), temperature management of the light source is difficult. Namely, an apparatus that uses a plurality of light sources has an advantage: even when any one of the light sources has a problem that causes a failure in lighting, the projected image will not be discontinued if the remaining light source is kept lightened. On the other hand, the conditions for lighting the light sources will be complicated. In such a case, it is important to review the temperature management of light sources, with reference to the mutual influences among the plural light sources. Conventionally however, for the temperature management of light sources, only an example of reviewing a method of controlling a cooling fan for a single light source has been known (see JP 2006-106409 A for example).
In a case of using a plurality of light sources so as to combine output light from the respective light sources and radiate the display device thereby projecting an image, it should be noted that an idle component that disperses or performs unnecessary radiation is included in addition to the effective component of the output light that is combined and used as the effective light. For example, in an apparatus that combines output light from the plural light sources, a part of the output light does not function as an effective light but it radiates an opposing light source so as to raise the temperature of the thus irradiated light source. This will cause problems such as whitening of the light sources and life property degradation.